Ever since the introduction of xerographic photocopiers, many have experienced the difficulty in producing clear, non-distorted copies from opened books or volumes that have been pressed upon the flat document glass. This difficulty is mainly due to the fact that conventional photographic copiers are designed for producing copies from documents (generally, single sheets) that lay flat upon the document glass. Textbooks with hard bindings cannot be so oriented.
The crease of a typical textbook generally pyramids upwardly away from the glass, thus causing an upside-down, "V-shaped" surface. This is especially so for thick books with hard covers. The crease, therefore, falls outside of the focal length range for which the copier lens can properly project the image of the book onto the image receiving medium or pre-charged paper. In other words, the crease cannot be focused properly to provide an undistorted image. As a result, the copied crease is often blurred, distorted, and often darkened.
In order to make the copies more legible, the operator of the copier is required to forcibly press upon the backing of the book as it rests upon the glass. Sometimes this will work. However, many times the binding is too stiff, and the crease cannot be projected into the fold. Pressing with excessive force is also risky, as this may cause damage to the binding. In some cases, an immoderate force may even break the glass.
The present invention reflects the discovery that the aforementioned problem can be solved in a user friendly and inexpensive manner.
The current invention comprises a corrective lens that is shaped to fit in the space between the book pages to be copied and the document glass of the copier. This simple solution provides a surprisingly unblurred and undistorted image of the adjacent pages of the book extending into the fold of the crease.